The human placenta is known to synthesize at least three polypeptide hormones: human placental lactogen (HPL -- also called human chorionic somatomammotropin), human chorionic gonadotropin (HCG) and human chorionic thyrotropin (HCT). The blood levels of each of these hormones change in a characteristic way during gestation and during the development of various trophoblastic diseases. However, the biochemical events by which the placental synthesis of these hormones is regulated are unknown. We intend to study key biochemical parameters of gene expression and protein synthesis in the human placenta in order to determine which processes or elements of the protein synthesizing machinery are responsible for the observed changes. These studies will be carried out for each of the three hormones, at different gestational ages and during the occurrence of certain placental pathologies. In particular, we will study protein hormone levels in placental tissue, protein hormone turnover rates, the levels of hormone-specific messenger RNAs, the turnover rates of these mRNAs, the number of initiation sites for hormone-specific mRNA transcription in chromatin and the number of hormone-specific gene copies in DNA. Measurement of these parameters will permit us to determine which of the events surrounding transcription and translation are of primary importance. Hormone levels and hormone synthesis will be determined by the use of radioimmunoassays; hormone specific mRNAs will be purified, evaluated through the use of a wheat germ in vitro protein synthesizing system, and assayed by the use of labeled complementary DNA. The number of initiation sites will be estimated through a labeled nucleoside "pulse" experiment followed by use of rifamycin to block reinitiation of transcription. The number of hormone-specific gene copies will be estimated by cDNA-DNA hybridization. These studies will permit us to elucidate the mechanisms by which regulation of placental synthesis of polypeptide hormones is effected, and thereby will provide insight into the role and control of placental polypeptide hormones during gestation and the onset of trophoblastic disease.